[jira] [Commented] (FLINK-23190) Make task-slot allocation much more evenly

["Piotr Nowojski (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/FLINK-23190?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17374789#comment-17374789 ] 

Piotr Nowojski commented on FLINK-23190:
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[~loyi] have you tried the [cluster.evenly-spread-out-slots|https://ci.apache.org/projects/flink/flink-docs-release-1.13/docs/deployment/config/#cluster-evenly-spread-out-slots] config option?

> Make task-slot allocation much more evenly
> ------------------------------------------
>
>                 Key: FLINK-23190
>                 URL: https://issues.apache.org/jira/browse/FLINK-23190
>             Project: Flink
>          Issue Type: Improvement
>          Components: Runtime / Coordination
>    Affects Versions: 1.12.3
>            Reporter: loyi
>            Priority: Major
>
> FLINK-12122 only guarantees spreading out tasks across the set of TMs which are registered at the time of scheduling, but our jobs are all runing on active yarn mode， the job with smaller source parallelism offen cause load-balance issues. 
>  
> For this job:
> {code:java}
> //  -ys 4     means 10 taskmanagers
> env.addSource(...).name("A").setParallelism(10).
>  map(...).name("B").setParallelism(30)
>  .map(...).name("C").setParallelism(40)
>  .addSink(...).name("D").setParallelism(20);
> {code}
>  
>  Flink-1.12.3 task allocation: 
> ||operator||tm1 ||tm2||tm3||tm4||tm5||5m6||tm7||tm8||tm9||tm10||
> |A| 1|{color:#de350b}2{color}|{color:#de350b}2{color}|1|1|{color:#de350b}3{color}|{color:#de350b}0{color}|{color:#de350b}0{color}|{color:#de350b}0{color}|{color:#de350b}0{color}|
> |B|3|3|3|3|3|3|3|3|{color:#de350b}2{color}|{color:#de350b}4{color}|
> |C|4|4|4|4|4|4|4|4|4|4|
> |D|2|2|2|2|2|{color:#de350b}1{color}|{color:#de350b}1{color}|2|2|{color:#de350b}4{color}|
>  
> Suggestions:
> When TaskManger start register slots to slotManager , current processing logic will choose  the first pendingSlot which meet its resource requirements.  The "random" strategy usually causes uneven task allocation when source-operator's parallelism is significantly below process-operator's.   A simple feasible idea  is  {color:#de350b}partition{color} the current  "{color:#de350b}pendingSlots{color}" by their "JobVertexIds" (such as  let AllocationID bring the detail)  , then allocate the slots proportionally to each JobVertexGroup.
>  
> For above case, the 40 pendingSlots could be divided into 4 groups：
> [ABCD]: 10        // A、B、C、D reprents  {color:#de350b}jobVertexId{color}
> [BCD]: 10
> [CD]: 10
> [D]: 10
>  
> Every taskmanager will provide 4 slots one time, and each group will get 1 slot according their proportion (1/4), the final allocation result is below:
> [ABCD] : deploye on 10 different taskmangers
> [BCD]: deploye on 10 different taskmangers
> [CD]: deploye on 10  different taskmangers
> [D]: deploye on 10 different taskmangers
>  
> I have implement a [concept code|https://github.com/saddays/flink/commit/dc82e60a7c7599fbcb58c14f8e3445bc8d07ace1]  based on Flink-1.12.3 ,  the patch version has {color:#de350b}fully evenly{color} task allocation , and works well on my workload .  Are there other point that have not been considered or  does it conflict with future plans?      Sorry for my poor english.
>  
>  



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